Tube rolling mill for producing tubing with various external configurations

ABSTRACT

A tube rolling mill having two sets of three rolls each which are reciprocatingly driven along a length of a tube supported by a mandrel. Each roll is forced against the tube by individual cams that each have a surface of one or more tapers to provide controlled reduction in wall thickness of the tube. If the mandrel is tapered, a reduction of inside tube diameter is accomplished. Various shapes in which at least a portion of the outside wall of the tube is flat are produced and totally flatsided-outer-wall tubing may be produced with the finished tubing having external cross-sectional configurations such as triangular, hexagonal or nonagonal configurations.

drel

is acportion produced and ay be produced forced 1 Oct. 22, 1974 Washburn,

3,178,924 4/1965 McC1e1lan................. 3,360,974 1/1968 Purvance.............. 3,570,582 3/1971 Clames 3,611,775 10/1971 Gabel et a1. Primary Examiner-Milton S. Mehr Attorney, Agent, or Firm-Woodcock Kurtz & Mackiewicz [57] ABSTRACT A tube rolling mill having two sets of three rolls each which are reciprocatingly driven along a length of a tube supported by a mandrel. Each roll is against the tube by individual cams that each hav surface of one or more tapers to provide controlled reduction in wall thickness of the tube. 1f the man is tapered, a reduction of inside tube diameter complished. Various shapes in which at least a of the outside wall of the tube is flat are totally flat-sided-outer-wall tubing m .1 a mn 0 3 rw m a u e m m 3 .1

,mm F v g a n h m m b i umm i. r. a 3; t m mm mem n 2 fi a D o e hnaa .mo m m wwo 3449 9220 TUBING WITH VARIOUS EXTERNAL CONFIGURATIONS [75] Inventor: Fred W. Bibighaus, Wapakoneta,

Ohio

Assignee: Superior Tube Company,

Norristown, Pa.

Oct. 18, 1972 Appl. No.: 298,617

.. 72/208, 72/220, 72/224 B2lb 17/06 72/208, 209, 193, 476, 72/224 X, 214, 220

References Cited UNITED STATES PATENTS Elaie States Patent [191 Bi ighaus 41 TUBE ROLLING MILL FOR PRODUCING [221 Filed:

[52] U.S.Cl...........

[51] Int.

[58] Field of Search 4/1881 9/1903 l/1950 2,603,114 7/1952 3 176 493 4/1965 Weissum.

PAFENIEU 3.842.635 sum 11: s

mamma 7 3. 842

an: as s RMIN. RMAX.

man a JL PAIENTEDBBTZZIBM 1 TUBE'ROLLING MILL FOR PRODUCING TUBING WITH VARIOUS EXTERNAL CONFIGURATIONS BACKGROUND OF THE INVENTION The subject invention improves upon and develops further in some respects the teachings of U.S. Pat. No. 3,688,540 which issued Sept. 5, 1972; U.S. Pat. No. 3,683,661 which issued Aug. 15, 1972; and U.S. Pat. No. 3,611,775 which issued Oct. 12, 1971.

This invention relates generally to a method and apparatus for reducing and elongating metal tubing and more particularly to a method and apparatus for producing externally configurated tubing by a tube reducing process employing cold rolling.

Metal tubing is used in a wide variety of environments and for many different applications. This requires that tubing be available with a wide variety of inside and outside diameters and wall thicknesses. Furthermore, certain applications require that the tube be provided with outer walls of different configurations from the more standard cylindrical tubing. In order to effectively utilize the economies of mass production, metal tubing is initially cylindrical in shape and manufactured in only a few standard sizes. This makes it necessary to modify tubing of a standard manufactured size to obtain a finished tube having an overall size and an external configuration that is needed for a certain application requiring less tubing than can be economically manufactured directly.

A machine for reducing tubing of a standard manufactured size with two rolls and a mandrel is described by Krause in the Iron and Steel Engineer, August, 1938, pp. 16-29, and in several patent publications such as U.S. Pat. Nos. 2,161,064, 2,161,065 and 2,223,039. In addition, there have been several disclosures by the Argonne National Laboratories relating to similar machines. Also, several publications by Russian authors have described tube rolling mills having three or six rolls. However, it is not known that any of these disclosures suggest a practical way of producing externally configurated tubing by a cold rolling process.

Therefore, it is an object of this invention to provide a tube rolling mill capable of rolling the exterior wall surface of tubing into various configurations.

It is also an object of this invention to provide a method of rolling the exterior wall surface of tubing into various configurations by cold rolling.

It is a further object of this invention to provide a method and apparatus for rolling the exterior wall surface of a tube into various configurations while simultaneously reducing the tubes wall thickness and/or its inside diameter thereby greatly increasing overall production rates by the simultaneous operation.

It is a still further object of this invention to provide a method of rolling tubing to produce exterior wall surfaces of flat sided configurations such as triangular, hexagonal and nonagonal shapes.

SUMMARY OF THE INVENTION These and additional objects are accomplished by a technique according to this invention in which a plurality of rolls are reciprocated back and forth along the length of a standard size manufactured tubing. Each of the rolls have tube contacting surfaces of various configurations for shaping the tubing. The plurality of rolls is held by a common rollhousing which is reciprocated against the tube which causes metal of the manufactured tubing to flow into a desired new configuration as the tube s wall thickness and/or inside diameter is being reduced. The plurality of rolls are positioned so that their tube contacting surfaces surround the tube being reduced and work all portions of the tube-outside surface, leaving no clearance between the contacting surfaces of the adjoining rolls. Neither the tube nor mandrel is rotated during the reduction and shaping process.

In a preferred form of the invention, three rolls are utilized in a cluster about the tube with their axes of rotation located in a plane substantially perpendicular to the tube and displaced from each other. Each roll is rotatably attached to a roll housing. The roll is urged against the tube by a pair of cam tracks on which roll trunnions ride. Within the roll housing, means are provided to insure that the rolls contact the cams at all times.

In a preferred form of the invention as described hereinafter, the tubing is shaped in conjunction with either wall thickness reduction or inside diameter reduction, or both, to obtain and externally configurated tube that is dimensioned exactly as required for a particular application. In order to obtain a good quality tubewith either wall thickness or inside diameter reduction, or both, it is preferred to use two sets of three roll clusters with a fixed spatial relationship within a roll housing. The axes of rotation of the rolls of one set (cluster) are displaced 60 from the axes of rotation of the rolls of the other set.

Tubing is shaped on its external surfacesaccording to the techniques of the present invention by the use of rolls which each have one or more flat tube contacting surfaces. Assuming that clusters of three rolls are used if the tube contacting surface of each roll is flat throughout from one side of the roll to the other a tube of triangular configuration will be produced. If each of the tube contacting surfaces of the rolls is formed by two intersecting flat surfaces, then tubing having a hexagonal configuration is produced. If each of the rolls has a tube contacting surface which is formed by three sides, a tube will be produced with an external nonagonal configuration.

In forming such shaped tubing according to the techniques of the present invention, the tube is preferably supported by a mandrel inside thereof. The mandrel may have a substantially uniform cross-section along a length in which the tube is worked, thus resulting in a general wall thickness reduction. Alternatively, the mandrel may have a significant taper for reducing the inside diameter of a tube simultaneously with the shaping of the external surface.

Shaped tubing may be produced by the techniques of the present invention with a wide variety of metals including those considered generally hard to work such as stainless steel, AISI types 304 and 316.

The techniques of the present invention are described in more detail hereinafter with respect to the drawings which show a preferred embodiment utilizing two roll clusters of three rolls each and a tapered mandrel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified partially exploded view showing essential elements of a rolling mill in which the present invention is utilized although the rolls as shown are used to produce tubing having a cylindrical external surface.

FIG. 2 is a cross-sectional view of FIG. 1 taken through the first stage (set) of rolls at 2-2;

FIG. 3 is a cross-sectional view of FIG. 1 taken through the second stage (set) of rolls 3-3;

FIG. 4 schematically illustrates the operation of the primary operating components of the rolling mill illustrated in FIGS. 1, 2 and 3;

FIG. 5 is for background purposes and shows the shape of a tube contacting groove of a roll for use in producing cylindrical tubing in the rolling mill shown in FIGS. l-3;

FIG. 6 illustrates the use of rolls of the subject invention having two flat sides to produce hexagonal tubing as shown;

FIG. 7 illustrates the use of rolls in which each roll is flat throughout its tube contacting surface to produce tubing of triangular configuration;

FIG. 8 illustrates the forming of nonagonal tubing by the use of rolls each having three flat tube contacting surfaces; and

FIG. 9 shows the operation of a cluster of four rolls operating against a tube according to yet another aspect of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a cam housing 11 is reciprocated relative to a machine frame 13 along a slide 15 in substantially a straight line. An electric motor 17, also attached to the frame 13, drives a flywheel 19. A rod 21 (partially broken away) is connected between the flywheel 19 at a crank pin 20 and the cam housing 11 to convert rotary motion of the flywheel to reciprocable motion of the cam housing. Within the cam housing 11 is a reciprocatable roll housing 23, shown removed from the cam housing for clarity of illustration. A pinion gear engages a rack 27 that isrigidly attached to the frame 13. A second pinion gear 26 engages a rack 29 that is rigidly attached to the cam housing 11. The pinion gears 25 and 26 are concentric about a common axis of rotation 30 and are nonrotatable relative to each other. The reciprocable motion of the axis of rotation 30 of the pinion gear 25 is communicated to the roll housing 23 by means of a connection rod 31 (shown herein as two sections since the roll housing 23 is shown removed from the cam housing 11). The cam housing 11 hasa maximum reciprocation stroke distance that is equal to the diameter of the circular path taken by the crank pin 20. From the geometry of the driving arrangement of FIG. 1, the roll housing 23 has a maximum reciprocation stroke distance that is equal to the maximum stroke of the cam housing 11 multiplied by the diameter of the pinion gear 25 and then divided by the sum of the diameters of the pinion gears 25 and 26. The use of two pinion gears having different radii as herein has the effect of increasing the length of the working zone along the tube without increasing the stroke length of the cam housing. It should be noted that although the double pinion gear arrangement herein is very convenient for controlling the maximum 4, relative cam housing and roll housing stroke distances, and thereby their relative velocities, other specific mechanical arrangements, such as one employing levers, may also be employed for the same purpose.

Another aspect of the geometry of this arrangement in FIG. 1 is that the cam housing stroke distance is equal to the sum of the roll housing stroke and the working stroke length of the cams (the distance along each cam that contacts a roll trunnion) within the cam housing. It follows, then, that the cam length contacted by each roll bears the same relationship to the roll housing stroke as a ratio of the diameter of the cam housing pinion gear 26 to the diameter of the roll housing pinion gear 25.

A tube 33 to be reduced and shaped according to the present invention is inserted through an opening 35 of the roll housing 23, and is carried by a mandrel 37. The mandrel 37 may be secured to the machine frame 13 by an appropriate gripping device 36, which also provides for removing the mandrel. An appropriate apparatus 38 is provided for positively gripping the tube 33 and linearly advancing (feeding) it over a working length of the mandrel 37. The apparatus 38 is also designed to rotate the tube at specific positions of the reciprocating cycle in which case the mandrel will also be rotated in order to produce smooth tubing of reduced size. However, in order to construct tubing with configurated external surfaces according to the present invention, neither the tube nor the mandrel is rotated.

FIGS. 2 and 3 better show the relationship of tube deforming rolls and the cam housing as sectional views of FIG. 1. A first set of rolls 39, 41 and 43, shown in FIG. 2, are held in the roll housing 23 with their axes of rotation lying substantially in a plane perpendicular to the mandrel 37 and making an angle of with each other. Similarly, a second set of rolls 45, 47 and 49, shown in FIG. 3, are held by the roll housing 23 in the position that their axes of rotation lie substantially in a plane perpendiculat to the mandrel 37 and at a spatially fixed distance along the length of the mandrel from the plane in which the axes of rotation of the first set of rolls 39, 41 and 43 lie. Furthermore, the axes of rotation of the two sets of rolls are angularly displaced from each other by 60. It should be noted that the rolls shown in FIGS. 1, 2, and 3 are designed to produce tubing with a cylindrical external surface.

Although held by the roll housing 23 against movement relative thereto in the direction of its reciprocation, each roll is free to move in a direction normal to the mandrel. Each roll is resiliently urged by a set of springs (such as springs 49 and 50, each held within a roll guide) out of the roll housing 23 and against its associated cam surfaces. Alternatively, the rolls may be hydraulically urged against their associated cams. Each roll has a trunnion formed on either side thereof, such as trunnions 51 and 53 on either side of the roll 45. Each roll is associated with a pair of cam tracks upon which its pair of trunnions ride. The two cams associated with each roll are designated herein with the same number as the roll but with an asterisk placed after the number referring to the other of the cam tracks. The

- cams are long metal bars shaped in a manner discussed hereinafter and rigidly attached to the cam housing 11. This attachment is accomplished through a recessed member for each pair of cams, such as a recessed member 55 which is shaped to support the cams 45* and 45. NOtice that the cams 45* each have a sloped side surface which allows fastening them to the recessed member 55 by a wedge 57 which is attached to the recessed member by a threaded fastener 58.

It should be noted with reference to FIGS. 1, 2 and 3, the ease with which the cam surfaces may be replaced in the cam housing 11 and also the ease with which the rolls may be replaced in the roll housing 23. A given pair of cams are removed by removing their associated wedge. The rolls are merely lifted out of the roll housing 23 when the roll housing is removed to a position as illustrated which is out of the cam housing 11. The mandrel 37 is also easily removed. These features allow quick conversion of the tube rolling mill to receive raw tubes of various sizes and also to produce finished tubes with various wall thicknesses and inside diameters.

The schematic diagram of FIG. 4 illustrates operation of the rolling mill illustrated in FIGS. 1, 2 and 3. The mandrel 37 is shown in cross-section along its length which includes a tube working zone B-J wherein at all points therealong the tube 33 is contacted by one or both sets of rolls to accomplish reduction either in wall thickness or inside diameter or both. The mandrel has a diameter d at its large end which is something slightly less than the inside diameter of the starting tube 33, thereby allowing the tube to be slid easily over the mandrel. The small end of the mandrel has a diameter d which is substantially equal to the desired inside diameter of the reduced tube. The mandrel 37 is gradually tapered within the tube working zone from one of these diameters to the other. This taper is significantly in excess of that required for tube relief. The diameters d, and d may differ by or percent or more, depending on the tube inside diameter reduction desired.

In order to demonstrate the cooperation between the cams and the mandrel, one roll from each of the two sets of rolls is shown in FIG. 4 as if they operated in the same plane so that the relationship between them and their cooperation in reducing the tube are illustrated. Rolls 39 and 45 are illustrated in FIG. 4 along with their associated cams 39* and 45*, respectively. The axis of the first stage roll 39 reciprocates along the tube between positions A and l with a distance therebetween equal to the stroke distance of the roll housing 23 (not shown in FIG. 4) in which the roll 39 is journaled. Similarly, the axis of the second stage roll 45 reciprocates along the tube between positions D and K. The cams 39* and 45* are attached to the cam housing 11 (not shown in FIG. 4) and thereby are reciprocatably driven at a greater velocity than the axis of the rolls, as described hereinabove. The cam 39* contacts a trunnion attached to the roll 39 and the cam'45* contacts the trunnion 51 of the roll 45. The shape of the cams and of the mandrel determine the displacements of rolls downward against the tube to bring about a desired deformation of the tube. 1

Consider asingle working stroke wherein the rolls and cams of FIG. 4 movefrom their far left hand position to the far right and back again. This represents the extent of movement brought about by a single revolution of the flywheel 19 of FIG. 1. The roll 39 begins at the position A and the roll begins at the position D. As shown by the dashed lines, the roll 39 contacts the tube3 fg thefirst time at about the pgsition B and the roll 45 contacts the tube 33 for the first time at approximately the position F. Proceeding further to the right, the cooperative shapes of the cams and the mandrel allow the roll 39 to be lifted from the tube 33 at bQEEfllQPQSIiQP.EdifiQW by the t 1 ihs roll, away from the tube. Similarly, the roll 45 is caused to be lifted from the tube 33 at about the position J, as

' the cam 39*, the cam working length thereof is the horizontal distance between points A, and I The tube 33 is advanced (fed) by the apparatus 38 an increment to the right while the rolls are drawn away from contact with the tube, either at one or both ends of the working stroke. As a variation in the system shown in FIG. 4, the cams 39* and 45* may be altered so that the rolls 39 and 45 are not drawn away from the tube at positions I and K, respectively, and the tube is fed only at the beginning of the working stroke. The shape of the tube 33 shown in FIG. 4 within the working zone represents the finished shape thereof after working stroke and before the tube is fed an increment in preparation for the next working stroke.

There are many specific cam and mandrel shapes that may be utilized depending upon the specific tube reduction desired. FIG. 4 illustrates a preferred arrangement for major inside diameter reduction. The following tabulation describes the work done by the roll 39 within the working zone between lettered positions along the length of the tube:

Between B-C: The tube is reduced to intimate contact with the mandrel.

Between C-E: Primarily tube diameter reduction is accomplished by the roll 39. Between E-F: Primarily wall reduction is accomplished by the roll 39.

The following tabulation describes the work concurrently performed by the roll 45 within the working zone between lettered positions along the length of the tube:

Between F-G: Primarily wall reduction performed by the roll 45.

Between G-;I-l: Primarily wall reduction performed by the roll 45 but with a lesser bite into the tube than between F-G.

Between I-I-J: This is a finishing zone where there is substantially no taper to the mandrel 37 and with very little bite of the roll into the tube.

To accomplish the above-noted specific tube reductions at various points within the tube working zone, the mandrel has one or more straight line tapers. The cams are shaped cooperatively therewith, each having a plurality of straight line tapers. The cams of FIG. 4 have their roll contacting surfaces marked with subscripted letters corresponding to the lettered positions along the tube. For example, when the roll 39 is positioned at E along the tube, the cam 39* is contacting the trunnion at position E Straight line-tapers are preferred for the cams and the mandrel since they are easy to machine, although continuous curves may also be employed.

shown by t hc path [45] of the roll, away from the H138.

The description herein with respect to FIG. 4 is exemplary only with various changes in the specifics thereof being possible. For example, if major inside tube diameter reduction is not required, the portion B,-F, of the cam 39* may be shaped differently relative to the portion B-F of the mandrel than as shown to effect tube wall reduction between B-F instead of tube diameter reduction. Also, the elements may be designed so that the rolls 39 and 45 overlap in their work zones along a portion of the tube, preferably with dissimilar cam tapers acting on the two rolls in this common length of the tube. Also, certian applications may require only a single taper along a working length of each of one set of cams. Furthermore, in those cases where little inside diameter reduction is desired, the cams and rolls described herein may be used with a mandrel having little or no taper.

Along any of the portions of the tube length wherein substantial wall thickness reduction is desired, the controlling cam and mandrel tapers are designed for a bite of the rolls into the tube at each point within this portion that is approximately the same percentage of the wall thickness at that point before the roll. Multiple straight line tapers on the cams may be employed to approximate this constant percentage although continuous curved cam surfaces are more exact. The amount of tube feed for each stroke is then adjusted to a maximum for a given tube material just short of that which ruptures the tube, thereby maximizing productivity of the machine.

In the production of reduced cylindrical tubing a tube contacting groove as illustrated in FIG. is used for the rolls of a rolling mill illustrated with respect to FIGS. 1-3. The groove shape is uniform in crosssection at any radial plane thereof. The groove crosssection is shown on a roll 79 which represents relative roll groove dimensions for any roll shown in FIGS. 1-3 for the purpose of describing roll groove design. In the center of the groove is an arcuate portion 81 having a center of curvature at a point 83.Joining either side of the arcuate center portion 81 as tangents thereto at its end points 85 and 87 are straight line segments 89 and 91 which extend to the groove outside edges 97 and 99, respectively. The arcuate portion 81 extends for an angular distance d) on either side of a center line.

The radius of curvature of the arcuate portion 81 is made substantially equal to or slightly less than the smallest outside tube radius the roll is designed to contact, such outside tube radius being represented by a solid circle 93. This represents a desired radius of the finished tube for the roll 45 shown in FIG. 4 and the radius of the tube at location F for the roll 39. A circle 95 (FIG. 5) represents the largest outside tube radius which the roll groove is designed to contact, that of the beginning tube for the roll 39 of FIG. 4 and that of the tube at position F for the roll 45.

This roll groove design provides two zones of contact for each roll against the outside of the tube between the tubes larger portion (95) and substantially until its smallest portion (93). Such two-zone rolling accomplishes more reduction in a given working zone of a tube when compared to a roll groove providing only one zone of contact with the tube. Furthermore, nonuniform tube wall strain is reduced as well as resulting degradation of tube quality. Also, required rolling forces, and this machine wear, are reduced. To optimize these advantages, the radius of the arcuate center portion 81 of the roll groove may be made 1 or 2 percent less than the smallest outside tube radius to be contacted by the roll groove, thereby extending two zone rolling over the entire length of the tube contacted by the roll, whereby roll like is extended. FIG. 5 illustrates such a preferred roll that is designed to contact the tube at two zones throughout the stroke. A rolling radius r of the roll 79 along the tube varies between Rm",r (contacting tube portion and R (contacting tube portion 93) during each tube reducing stroke. An arcuate center portion 81 with a radius significantly smaller than the finished tube outside radius (in the extreme the groove becomes V-shaped) results in a finished reduced tube surface that is irregular and rough.

For a given tube material, there is an optimum angle (1) which allows the roll to take the most efficient maximum bite into the tube, thereby resulting in the most rapid feed rate of the tube through the machine. An angle 0) of from 30-38 degrees is satisfactory for most common tube materials and specific types of reduction.

The tangential portions 89 and 91 of the roll groove are shown in FIG. 5 as straight lines. However, these portions of the groove may, alternatively, be given a curvature with one or more finite radii of curvature.

The rolling mill using the rolls described and shown in FIGS. 1-3 and 5 is used for producing a cylindrical finished tube with a smooth surface which is achieved by rotating the tube at least once each working stroke at a position thereof where the rolls do not contact the tube. Externally configurated tubing in which the external surface is rolled to have at least one fiat side is produced by substituting rolls as will be described with respect to FIGS. 6-9 for the rolls of FIGS. 1-3 and 5 and modifying the process by not rotating the tubing at all during the working stroke.

In FIG. 6 rolls are shown which will produce finished tubing 201 having an external hexagonal configuration. A second stage cluster of :rolls 245, 247 and 249 are shown which are driven in the manner of rolls 45, 47 and 49 as described in FIG. 3. The tube contacting surface of each roll, however, differs from the tube contacting grooves of the rolls as described above, and is V-shaped with each roll having two flat portions as viewed endwise of the roll and as considered in terms of impact relation to the tube as shown by portions 202 and 203 of roll 245 which extend circumferentially around the roll and which intersect in the center of the roll thus forming the tube contacting surface. As seen in FIG. 6, each roll 245, 247 and 249 will form two sides of the hexagonal finished tube 201. A mandrel 204 corresponding to mandrel 37 as previously described may be used with the rolls 245, 247 and 249. The mandrel may be tapered only slightly or not at all so that there is no appreciable inner diameter reduction; or it may be tapered significantly to produce inner diameter reduction as well as wall reduction.

FIG. 6 has been described as if only a single set of rolls 245, 247 and 249 were operating against the tube. However, for effecting a significant tube inside diameter reduction with a tapered mandrel at the same time that the tubing is shaped into its hexagonal exterior configuration, both roll stages shown in FIGS. 1-4 are preferably utilized. The first stage rolls are positioned so that one roll will form sides A and B, the second roll will form sides C and D, and the third roll will form sides E and F. Since the second set of rolls are displaced 60 from the first set, one roll of the second set will operate on sides B and C while the second roll operates on sides D and E and the third roll operates on sides F and A.

With respect to FIG. 7 rolls 210, 212 and 214 are used to produce triangular configurated tubing 216 in a fashion similar to the production of hexagonal tubing in FIG. 6. It will be noted that the tube contacting surface 218 of roll 210 is flat across its width and when rolls 212 and 214 are provided with similar tube contacting surfaces, the three sided substantially equilateral tube 216 is produced. A mandrel 219 of the variety as described in FIG. 1 may be used. As in the case of the description with FIG. 6, FIG. 7 has been described as if only a single set of rolls 210, 212 and 214 were operating against the tube. For effecting significant tube inside diameter reduction at the same time as the tubing is shaped both rolling stages shown in FIGS. 1-4 are preferably utilized. It will be noted, however, that the first stage rolls (not shown) which occupy the same position as rolls 39, 41 and 43 of FIGS. l-4 will form three angles spaced 120 around the tube at spaces at the intersections of the rolls. These angles as formed by the first stage rolls are displaced 60 from each of the angles that are formed by the second stage rolls 21(1), 212 and 214. Thus the angles formed by the first stage rolls are flattened or rolled out by the second rolls 210, 212 and 214 leaving only three angles as shown in FIG. 7 on the outside of the finished tube 216.

With reference to FIG. 8 rolls 220, 222 and 224 are 7 shown having tube contacting surfaces which may be used to produce nonagonal tubing 226. Each of the rolls have three flat tube contacting surfaces 228, 230 and 232 as shown on roll 220. Thus each of the rolls forms three sides of the nine sided figure. A mandrel 234 may be similar to mandrel 37 of FIG. I. As in the cases of FIGS. 6 and 7 the rolls of FIG. 8 may be used in conjunction with another set of rolls to provide two rolling stages as shown and described with respect to FIGS. 1-4. In this case as was the case with the triangular tubing of FIG. 7 the initial angles formed in the first roll stage are flattened out by the second stage rolls since the second stage rolls are displaced 60 from the first st grg W a The present invention has been described in its various aspects with reference to FIGS. l-8 in the environment of a rolling mill employing at least one cluster of three tube contacting rolls. It shall be understood that the invention is not limited to the use of only three rolls. For instance, a cluster of four rolls distributed around a tube to be reduced may be utilized as illustrated in FIG. 9. Rolls 240, 242, 244, and 246 each have one flat tube contacting surface extending around the entire tube contacting region. A mandrel 248, may be used of the same type as described in the other embodiments. A tube 250 having a square exterior configuration is thus produced.

It will be seen from the above embodiments that tubing having various external configurations may be produced during a rolling process in which the inner diameter of the tube is simultaneously reduced as the shaping is being done. As was previously noted, tubing is initially manufactured in a limited number of diameters. For many applications the inner diameter of the tube must be reduced and the outer wall shaped to provide various external configurations. As disclosed above,

both of these tube modifications can be performed simultaneously as distinguished from previously known processes in which two distinct operations were necessary to provide tubing having characteristics as described herein. Higher production and savings in time and operational expenses are thus realized.

It shall be understood that the invention is not limited to the specific arrangements described herein and the preferred embodiments, but the changes and modifications may be made within the scope of the appended claims.

I claim:

1. A method of producing flat sided externally configurated tubing from cylindrical tubing by cold rolling comprising the steps of:

positioning a mandrel within a cylindrical tube, the

mandrel having a taper between spaced locations along its axis defining a working zone. surrounding the tubing by tube contacting surfaces of a first plurality of rolls and a second plurality of rolls at spaced locations within the working zone along the axes of the tube and mandrel, the axes of rotation of the rolls at each of the spaced locations lying in common planes that are perpendicular to the axes of the tube and mandrel, the rolls in the second plurality each having at least one flat portion for contacting and shaping the outer surface of the tube,

reciprocating all of the rolls longitudinally of the tube through the working zone between a first position and a second position,

guiding the first plurality of rolls along a predetermined path through the working zone concurrently to move the rolls of the first plurality toward the axis of the tube and into contact with the outer surface thereof as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force from all sides on the tube and against the mandrel to cause metal in the wall of the tube to flow whereby the inside diameter and wall thickness of the tube are reduced,

guiding the second plurality of rolls along a predetermined path through the working zone concurrently to move the rolls of the second plurality toward the axis of the tube and into contact with the outer surface thereof as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force on the tube from all sides and against the mandrel to cause metal in the wall of the tube to flow thereby causing the outer surface of the tube to have flat sides as formed by the at least one flat portion of the tube contacting surface of each roll of the second plurality of rolls to produce the desired flat sided externally configurated tubing,

removing all of the rolls from contact with the tube at the end of the reciprocation, and

advancing the tube an incremental amount along the mandrel while maintaining the same rotational position of the tube.

2. A tube rolling mill for producing flat sided exter- 5 nally configurated tubing from cylindrical tubing by cold rolling comprising:

a mandrel having a taper extending between spaced locations along its axis defining a working zone,

and adapted to have placed thereover a cylindrical tube,

a first plurality of rolls within said working zone journaled in a roll housing at equidistant spaced locations around the axis of said mandrel and each of said rolls having a tube contacting surface, the axes of rotation of said rolls in said first plurality lying in a common plane perpendicular to the axis of said mandrel,

a second plurality of rolls within said working zone journaled in said roll housing at equidistant spaced locations around the axis of said mandrel and having their axes of rotation lying in a common plane perpendicular to the axis of said mandrel and spaced from said common plane of said first plurality of rolls, each of said rolls in said second plurality having at least one flat portion for contacting the outer surface of a tube on said mandrel,

means for reciprocating said roll housing through said working zone along the working length of said mandrel between a first position and a second position,

means for guiding said first plurality of rolls along a predetermined path through the working zone concurrently to move said rolls of said first plurality toward the axis of the mandrel and into contact with the outer surface of a tube as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force from all sides on the tube and against the mandrel to cause metal in the wall of the tube to flow whereby the inside diameter and wall thickness of the tube are reduced,

means for guiding said second plurality of rolls along a predetermined path through the working zone concurrently to move said rolls of said second plurality toward the axis of the mandrel and bring said flat portion of each of said rolls of the second plurality into contact with the outer surface of the tube as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force on the tube from all sides and against the mandrel to cause metal in the wall of the tube to flow thereby causing the outer surface of the tube to have flat sides,

said guiding means including means for removing all of said rolls from contact with the tube at the end of the reciprocation, and

means for advancing the tube an incremental amount along the mandrel while maintaining the same rotational position of the tube. 

1. A method of producing flat sided externally configurated tubing from cylindrical tubing by cold rolling comprising the steps of: positioning a mandrel within a cylindrical tube, the mandrel having a taper between spaced locations along its axis defining a working zone. surrounding the tubing by tube contacting surfaces of a first plurality of rolls and a second plurality of rolls at spaced locations within the working zone along the axes of the tube and mandrel, the axes of rotation of the rolls at each of the spaced locations lying in common planes that are perpendicular to the axes of the tube and mandrel, the rolls in the second plurality each having at least one flat portion for contacting and shaping the outer surface of the tube, reciprocating all of the rolls longitudinally of the tube through the working zone between a first position and a second position, guiding the first plurality of rolls along a predetermined path through the working zone concurrently to move the rolls of the first plurality toward the axis of the tube and into contact with the outer surface thereof as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force from all sides on the tube and against the mandrel to cause metal in the wall of the tube to flow whereby the inside diameter and wall thickness of the tube are reduced, guiding the second plurality of rolls along a predetermined path through the working zone concurrently to move the rolls of the second plurality toward the axis of the tube and into contact with the outer surface thereof as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force on the tube from all sides and against the mandrel to cause metal in the wall of the tube to flow thereby causing the outer surface of the tube to have flat sides as formed by the at least one flat portion of the tube contacting surface of each roll of the second plurality of rolls to produce the desired flat sided externally configurated tubing, removing all of the rolls from contact with the tube at the end of the reciprocation, and advancing the tube an incremental amount along the mandrel while maintaining the same rotational position of the tube.
 2. A tube rolling mill for producing flat sided externally configurated tubing from cylindrical tubing by cold rolling comprising: a mandrel having a taper extending between spaced locations along its axis defining a working zone, and adapted to have placed thereover a cylindrical tube, a first plurality of rolls within said worKing zone journaled in a roll housing at equidistant spaced locations around the axis of said mandrel and each of said rolls having a tube contacting surface, the axes of rotation of said rolls in said first plurality lying in a common plane perpendicular to the axis of said mandrel, a second plurality of rolls within said working zone journaled in said roll housing at equidistant spaced locations around the axis of said mandrel and having their axes of rotation lying in a common plane perpendicular to the axis of said mandrel and spaced from said common plane of said first plurality of rolls, each of said rolls in said second plurality having at least one flat portion for contacting the outer surface of a tube on said mandrel, means for reciprocating said roll housing through said working zone along the working length of said mandrel between a first position and a second position, means for guiding said first plurality of rolls along a predetermined path through the working zone concurrently to move said rolls of said first plurality toward the axis of the mandrel and into contact with the outer surface of a tube as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force from all sides on the tube and against the mandrel to cause metal in the wall of the tube to flow whereby the inside diameter and wall thickness of the tube are reduced, means for guiding said second plurality of rolls along a predetermined path through the working zone concurrently to move said rolls of said second plurality toward the axis of the mandrel and bring said flat portion of each of said rolls of the second plurality into contact with the outer surface of the tube as the rolls proceed from the first position to the second position during reciprocation thereby concurrently exerting force on the tube from all sides and against the mandrel to cause metal in the wall of the tube to flow thereby causing the outer surface of the tube to have flat sides, said guiding means including means for removing all of said rolls from contact with the tube at the end of the reciprocation, and means for advancing the tube an incremental amount along the mandrel while maintaining the same rotational position of the tube. 